Glass bulb for cathode-ray tube

ABSTRACT

With respect to a highly flat glass bulb for cathode ray tube having an effective screen diameter along a diagonal axis of a glass panel  10  of more than or equal to 500 mm, and an average radius of curvature of an outer surface of a face portion of more than or equal to 10,000 mm, a ratio between a length h of a skirt portion  13  of the glass panel and a distance H in the tube axis direction from an edge surface portion where a funnel is sealed with the glass panel to a reference line is defined so as to fall within a predetermined range in relation to a deflection angle θ of the funnel representing substantial degree of divergence in the tube axis direction of the funnel, thereby achieving reduction of weight of the glass bulb while maintaining a certain mechanical strength, as well as suppressing breakage during frit seal heating process.

FIELD OF THE INVENTION

The present invention relates to a glass bulb for cathode ray tube usedin a television and the like.

BACKGROUND OF THE INVENTION

As shown in FIG. 3, a glass bulb 1 for cathode ray tube generallycomprises a glass panel 10 serving as a front surface portion, a funnel20 serving as a back structural member and a neck 30 for mounting anelectron gun therein. The glass panel 10 includes a face portion 11 ofapproximately rectangular shape having an effective screen fordisplaying an image, and a skirt portion 13 continued from the peripheryof the face portion 11 via a blend R portion 12 and having a seal edgesurface portion 14 for sealing with the funnel 20.

The funnel 20 includes a top portion 22 extending nearly vertically inthe tube axis direction from a seal edge surface portion 21 for sealingwith the glass panel, a yoke portion 24 outside of which a deflectionyoke is to be attached, and an intermediate body portion 23 connectingthe top portion and the yoke portion. A reference line 25 existing inthe yoke portion is a hypothetical line used for indicating a referenceposition of the funnel. In the case of a color cathode ray tube, theglass panel 10 is sealed between the seal edge surface portion 14 of theskirt portion 13 and the seal edge surface portion 21 of the funnel 20via frit glass and the like. In this context, θ designates a deflectionangle in the yoke portion of the funnel 20, and is defined as an angleof divergence of an effective screen diameter D along the diagonal axisof the rectangular face portion 11 viewed from a hypothetical referencepoint on the reference line 25.

Since the above glass bulb 1 is used as a vacuum vessel of whichinterior is evacuated to vacuum, a stress caused by a pressuredifference between inside and outside of the bulb will act on the outersurface of the glass bulb 1. In the case of the glass bulb which is nota spherical shell, however, as shown in FIG. 2, there arises complicateddistribution of stress such that an area of tensile stress denoted byarrows toward outside of the bulb and an area of compressive stressdenoted by arrows toward inside of the bulb are present at the sametime.

The vacuum tensile stress generated in the glass bulb 1 usually becomesmaximum in end regions on the short axis of the glass panel 10, and whena mechanical or thermal shock exceeding a certain degree is applied tothe glass bulb 1 from the outside, the glass bulb 1 breaks from thevicinity of the region where the maximum vacuum tensile stress isgenerated, that is from the region ranging from the end of the faceportion 11 to the skirt portion 13 as its origin of breakage, resultingin implosion. Therefore, the glass bulb 1 used in a cathode ray tube isusually designed to have an enough mechanical strength to suppress thevacuum tensile stress to a predetermined value or less.

The distribution of vacuum tensile stress depends on the size and shapeof the glass bulb, and thus the shape, wall thickness and the like areusually designed so as to suppress the vacuum tensile stress generatedat the seal edge portion between the glass panel and the funnel to lessthan about 8.4 MPa, which is one standard of mechanical strengthrequired for a glass bulb determined in consideration of safety factorssuch as shocks applied from the outside.

For this reason, in conventional glass bulbs for cathode ray tube, inorder to suppress the vacuum tensile stress to less than thepredetermined value while maintaining the mechanical strength, suchmeasures have been taken as increasing the wall thickness of the panel,elongating the skirt portion for relieving and distributing the vacuumtensile stress generated in the vicinity of the skirt portion to therebyreduce the peak value thereof, and the like.

In conventional glass bulbs for cathode ray tube, however, since theweight of the glass is increased because of the increased wall thicknessof the panel or the elongated skirt potion, there is a problem that theglass bulb is inferior in operability and workability.

Moreover, the glass panel is formed by press molding of a molten glassgob and then gradually cooled to manufacture the glass panel of roomtemperature. However, during the continuous cooling process, delaycondition occurs in cooling degree of each portion because of thethree-dimensional box-shaped structure and uneven distribution of thewall thickness, so that the glass panel is usually cooled with thetemperature distribution being uneven, causing the portion whosetemperature has dropped below the temperature of the strain point tosequentially solidify. The strain point is the point that viscous flowof the glass is substantially stopped.

As a result, when the glass panel is brought to the room temperature,the distortion appears as warpage of the glass panel which willgenerally cause inward inclination in the vicinity of the seal edgesurface portion on the short axis and long axis of the glass panel andoutward inclination in the vicinity of the seal edge portion on thediagonal axis, and tensile stresses remain outside of the seal edgesurface portion on the diagonal axis.

Furthermore, also in the frit seal heating process at the time ofsealing the glass panel with the funnel, uneven temperature distributionoccurs within the glass panel and a temporary distortion which willcause the seal edge surface portion on the diagonal axis to inclineoutwardly occurs, resulting that a tensile stress is exerted and theglass tends to break due to the resultant with the remaining tensilestress at the time of the molding as described above. This tendency issignificantly problematic in a glass panel in which the skirt portion iselongated in a large panel having a flat face portion.

The applicant of the invention has applied an invention relating a glasspanel for cathode ray tube in which weight reduction is enabled byshortening the skirt portion while maintaining the mechanical strengthas a glass bulb for international patent (PCT/JP99/07135).

FIG. 6 shows a section in the short axis direction of the glass panelfor cathode ray tube which comprises the face portion 11 ofsubstantially rectangular shape, and the skirt portion 13 connected withthe periphery of the face portion via the blend R portion 12 and havingthe seal edge surface 14 for sealing with the funnel. In the aboveinternational patent application, the glass panel for cathode ray tubehaving the shape as shown in FIG. 6 is so configured that an effectivescreen diameter D(mm) of the glass panel along the diagonal axis thereofis in the range of 500≦D<650; an average radius of curvature of theouter surface of the face portion 11 is more than or equal to 10,000 mmin any radial direction passing the center of the face portion; and adistance h (mm) along the tube axis from a contact between the effectivescreen end of the inner surface of the glass panel and the blend Rportion 12 to the seal edge surface 14 at least along the short axis ofthe glass panel, and a glass wall thickness t(mm) of the seal edgesurface 14 satisfy the relationships of: 0.07D≦h≦0.11D, 0.015D≦t≦0.025Dand (D/25.4)²≦t×h≦(D/25.4+3)², or that the effective screen diameterD(mm) of the glass panel along the diagonal axis thereof is more than orequal to 650; the average radius of curvature of the outer surface ofthe face portion is more than or equal to 10,000 mm in any radialdirection passing the center of the face portion; and the distance h(mm) along the tube axis from the contact between the effective screenend of the inner surface of the glass panel and the blend R portion 12to the seal edge surface 14 at least along the short axis of the glasspanel, and the glass wall thickness t (mm) of the seal edge surface 14satisfy the relationships of: 0.08D≦h≦0.11D, 0.015D≦t≦0.020D and(D/25.4)²≦t×h≦(D/25.4+2.5)². In such a way, the above internationalpatent application suggests the technique for reducing the weight of theglass panel compared to the prior art by shortening the skirt portion13, while maintaining the mechanical strength as a glass bulb.

It is an object of the invention to provide a glass bulb for cathode raytube in which, by combining the condition of the glass panel for cathoderay tube suggested by the above invention of international patentapplication into a glass bulb for cathode ray tube having a glass panelwhich is large in size and having a flat face portion, properrelationship between the glass panel and the funnel in length along thetube axis direction is defined, reduction in weight is achieved byshortening the panel skirt portion while maintaining a certainmechanical strength as a glass bulb, a tensile stress which will occuroutside the seal edge surface portion on the diagonal axis is reduced,and breakage during frit seal heating process and the like issuppressed.

SUMMARY OF THE INVENTION

The present invention is featured in that, with respect to a highly flatglass bulb for cathode ray tube having an effective screen diameter inthe direction of a diagonal axis of a glass panel of more than or equalto 500 mm, and an average radius of curvature of an outer surface of aface portion of more than or equal to 10,000 mm, from the view point ofachieving reduction of weight of the glass bulb while maintaining acertain mechanical strength, as well as suppressing breakage during fritseal heating process, a ratio between a length h of a skirt portion ofthe glass panel and a distance H in a tube axis direction from an edgesurface portion where a funnel is sealed with the glass panel to areference line is defined so as to fall within a predetermined range inrelation to a deflection angle θ of the funnel representing substantialdegree of diversion in the tube axis direction of the funnel.

In specific, the present invention provides a glass bulb for cathode raytube comprising: a glass panel having a skirt portion continued from aface portion of approximately rectangular shape forming an effectivescreen via a blend R portion; a funnel having a reference line in a yokeportion, the funnel being sealed with the glass panel; and a neck sealedwith the funnel, to which an electron gun is attached, wherein aneffective screen diameter D (mm) along a diagonal axis of the faceportion of the glass panel is in the range of 500≦D<650; an averageradius of curvature of an outer surface of the face portion is more thanor equal to 10,000 mm in any radial direction passing the center of theface portion; and a length h (mm) of the skirt portion in a tube axisdirection from a contact between an end of the effective screen of aninner surface of the face portion and the blend R portion to an edgesurface portion where the glass panel is sealed with the funnel at leastalong a short axis of the glass panel, a deflection angle θ (°) of theyoke portion of the funnel, and a distance H (mm) in the tube axisdirection from an edge surface portion where the funnel is sealed withthe glass panel to the reference line satisfy the relationship of:1/(0.22 tan(θ/2))−1≦H/h≦1/(0.14 tan(θ/2))−1.

Alternatively, the present invention is characterized in that aneffective screen diameter D (mm) along a diagonal axis of the faceportion of the glass panel is more than or equal to 650; an averageradius of curvature of an outer surface of the face portion is more thanor equal to 10,000 mm in any radial direction passing the center of theface portion; and a length h (mm) of the skirt portion in a tube axisdirection from a contact between an end of the effective screen of aninner surface of the face portion and the blend R portion to an edgesurface portion where the glass panel is sealed with the funnel at leastalong a short axis of the glass panel, a deflection angle θ (°) of theyoke portion of the funnel, and a distance H (mm) in the tube axisdirection from an edge surface portion where the funnel is sealed withthe glass panel to the reference line satisfy the relationship of:1/(0.22 tan(θ/2))−1≦H/h≦1/(0.16 tan(θ/2))−1.

The reason why the specification of the length h of the skirt portion ofthe glass panel was made on the short axis of the glass panel is thatthe maximum vacuum tensile stress on the glass bulb is usually generatedin the region ranging from the end of the face portion to the skirtportion on the short axis, however, in the case of a panel having a flatface portion as described above, the length h of the skirt portionspecified on the short axis is substantially equal to those specified onthe long axis and the diagonal axis, and also substantially equal to thedistance in the tube axis direction from the inner surface of the centerof the panel to the panel seal edge surface portion.

Therefore, the effective surface diameter D of the glass panel along thediagonal axis is represented by D=2(H+h)tan(θ/2) by using the H and θ ofthe funnel and the length h of the skirt portion as defined above. Tothe contrary, in the suggestion in the invention of the above-mentionedinternational patent application, the range of the ratio between thelength h of the skirt portion of the glass panel and the effectivescreen diameter D of the glass panel along the diagonal axis is definedby the inequalities of 0.07≦h/D≦0.11 when the effective screen diameterD (mm) is in the range of 500≦D<650, and 0.08D≦h/D≦0.11 when theeffective screen diameter D (mm) is more than or equal to 650 from theview point of weight reduction and the strength.

In view of the above, a relation between the length h of the skirtportion of the glass panel and the distance H in the tube axis directionfrom the edge surface portion where the funnel is sealed with the glasspanel to the reference line is determined from the above inequalitiesand the above expressions of the effective screen diameter D, then theinequalities of H/h according to the present invention are derived. Inaddition, we confirmed that when the relationship in length between thepanel and the funnel in the tube axis direction falls in the rangedefined by the above inequalities, it is desirable also from the viewpoint of suppressing breakage from the outside of the seal edge surfaceportion on the diagonal axis of the glass panel.

In general, the wall thickness of the funnel is not more than about ahalf of that of the panel, and the wall thickness gradually decreasesfrom the seal edge surface portion to the yoke portion. Also thedistance from the tube axis is smaller in the body portion compared withthe seal edge surface portion. Therefore, in the bulbs having the samedeflection angle, by shortening the length of the skirt portion of thepanel in the tube axis direction and extending the length of the bodyportion of the funnel by the corresponding amount, it is possible toreduce the volume of the glass without changing the entire length of thebulb in the tube axis direction, so that weight reduction can beachieved.

Furthermore, another reason why the above dimension H of the funnel iscorrected by extending the body portion of the funnel is that the shapesand dimensions of the yoke portion of the funnel and the seal edgesurface portion are relatively fixedly defined in relation to outsideattachment of the deflection yoke and fitting with the panel,respectively, while on the other hand, the shape and dimension of thebody portion can be relatively freely designed because the body portionis the part constituting the vessel as a bulb.

In the case where the ratio H/h is 1/(0.22 tan(θ/2))−1>H/h, since thelength of the skirt portion is not reduced, it is impossible to reducethe weight of the glass bulb and the tensile stress in the seal edgesurface portion along the diagonal axis of the glass panel becomesrelatively large, so that it is impossible to sufficiently suppressbreakage caused by thermal shock at the time of subjecting the glasspanel and the funnel to a frit seal heating process and the like.

On the other hand, in the case where 500≦D<650 and H/h>1/(0.14tan(θ/2))−1 or where 650≦D and H/h>1/(0.16 tan(θ/2))−1, the length ofthe skirt portion is reduced too much, causing the vacuum tensile stressvalue of the seal edge portion generated by evacuation of the glass bulbto become more than 8.4 MPa, so that it is impossible to obtain adesired mechanical strength required for a glass bulb.

According to the glass bulb for cathode ray tube of the presentinvention, since the ratio between the length of the skirt portion ofthe panel and the length in the tube axis direction of the funnel is setin a proper range, that is, the length of the skirt portion of the panelwhich has conventionally been longer than needed is shortened to asuitable dimension while the body portion in particular of the funnel isextended by the corresponding amount to compensate the shortening,thereby accomplishing reduction of weight without changing the entirelength of the cathode ray tube, as well as maintaining the pressureresistance of the cathode ray tube at a necessary level, it is possibleto provide a glass bulb for cathode ray tube which is easy to handle andsuppresses the occurrence of breakage in the neighborhood of the sealingportion along the diagonal axis caused by thermal shock due to frit sealheating process and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view in short axial section of a glass bulb forcathode ray tube according to the present invention;

FIG. 2 is an explanatory view of distribution of vacuum stress generatedin the glass bulb for cathode ray tube;

FIG. 3 is an explanatory view of a glass bulb for cathode ray tube;

FIGS. 4 and 5 are graphs showing ranges of H/h set for glass bulbs forcathode ray tube having different sizes according to the presentinvention; and

FIG. 6 is an explanatory view in short axial section of a glass panelfor cathode ray tube used in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, a glass bulb for cathode ray tube according to thepresent invention will be described with reference to working examples.FIG. 1 is an explanatory view in short axial section of a glass bulb forcathode ray tube according to the present invention. The components assame as those described above will be denoted by the same referencenumerals and explanations thereof will be omitted.

In the drawing, the reference numeral “h” denotes a distance in the tubeaxis direction along the short axis of the glass panel 10 from a contactbetween the end portion of the effective screen of the inner surface ofthe face portion 11 and the blend R portion 12 to the seal edge surfaceportion 14, of the skirt portion 13 which is defined as the length ofthe skirt portion. The reference numeral “H” denotes a distance alongthe tube axis direction from the seal edge surface portion 21 of thefunnel 20 to the reference line 25.

Panels and funnels used for glass bulbs for cathode ray tube accordingto the present invention, and panels and funnels used for glass bulbs ofcomparative examples were individually manufactured and the weights ofthese panels and funnels were measured. After sealing the funnel and aneck to the corresponding glass panel to make a glass bulb, the air wasexhausted from the interior thereof, and then a vacuum tensile stressvalue of the seal edge portion of each glass bulb was measured by meansof a strain gauge.

A mechanical strength of the glass bulb was evaluated by measuring thevacuum tensile stress value generated at the seal edge portion.Additionally, before crystallizing the glass panel at about 440° C. for40 minutes which is a typical condition for heat treatment at the timeof frit sealing a glass panel and a funnel, the situation with regard tobreakage when the glass panel was heated from the room temperature toabout 440° C. at a temperature gradient of 12 to 13° C./min. wasmonitored as an acceleration test.

Tables of FIGS. 1 to 4 each show dimensions of portions of the glasspanels for cathode ray tube and the funnels, weights of the glass bulbs,values of vacuum tensile stress generated in the seal edge portion inthe form of a glass bulb and ratios of breakage at the time ofconducting the frit seal heating process. In each table, Samples 2, 3,4, 5, 7 and 8 are examples using the bulbs for cathode ray tubeaccording to the present invention, Sample 1 is a conventional exampleand Sample 6 is a comparative example. Sample 7 is an example where thedeflection angle is set at 110° and Sample 8 is an example where thedeflection angle is set at 103° or 90°.

Table 1 shows data for bulbs consisting of a panel having an effectivescreen diameter along the diagonal axis of the glass panel of 510 mm (21inches), an aspect ratio of 4:3 and a minimum average radius ofcurvature of the outer surface of the face portion of 33,000 mm andfunnels having deflection angels of 88°, 110° and 103°.

In the bulbs for cathode ray tube of Samples 2 to 5 according to thepresent invention, it was possible to reduce the weight by about 0.6 kgat the maximum compared to the conventional bulb for cathode ray tube asshown by Sample 1, and a desirable result was obtained that the vacuumtensile stress at the seal edge portion was less than the standard valueof 8.4 MPa for all Samples. Furthermore, the bulbs for cathode ray tubeof Samples 2 to 5 according to the present invention were able tosuppress the rate of breakage caused by thermal shock at the time offrit seal heating process better than the conventional bulb for cathoderay tube as shown by Sample 1. With regard to Samples 4 and 5, since thewall thickness of the seal edge portion was adjusted so as to suppressthe increase in vacuum tensile stress of the seal edge portion caused bythe shortening of the skirt portion, Samples 4 and 5 became heavier thanSample 3, but weight reduction compared to Sample 1 was realized.

With regard to Sample 6 which is a comparative example, though anattempt was made to adjust the wall thickness of the seal edge portionin order to suppress the increase in vacuum tensile stress of the sealedge portion caused by the shortening of the skirt portion, it wasimpossible to achieve the vacuum tensile stress of not more than 8.4 MPaat the weight lighter than that of Sample 1 which is a conventionalexample. With regard to Samples 7 and 8, the examples of the presentinvention where the deflection angle of the funnel is set at 110° and103°, respectively, they presented desirable results as is the case of88° according to the present invention.

Table 2 shows data for bulbs consisting of a panel having an effectivescreen diameter along the diagonal axis of the glass panel of 600 mm (25inches), an aspect ratio of 4:3 and a minimum average radius ofcurvature of the outer surface of the face portion of 30,000 mm andfunnels having deflection angels of 106°, 110° and 90°.

In the bulbs for cathode ray tube of Samples 2 to 5 according to thepresent invention, it was possible to reduce the weight by about 0.5 kgat the maximum compared to the conventional bulb for cathode ray tube asshown by Sample 1, and a desirable result was obtained that the vacuumtensile stress at the seal edge portion was less than the standard valueof 8.4 MPa for all Samples. Furthermore, the bulbs for cathode ray tubeof Samples 2 to 5 according to the present invention were able tosuppress the rate of breakage caused by thermal shock at the time offrit seal heating process better than the conventional bulb for cathoderay tube as shown by Sample 1.

With regard to Samples 4 and 5, since the wall thickness of the sealedge portion was adjusted so as to suppress the increase in vacuumtensile stress of the seal edge portion caused by the shortening of theskirt portion, Samples 4 and 5 became heavier than Sample 3, but weightreduction compared to Sample 1 was realized. With regard to Sample 6which is a comparative example, though an attempt was made to adjust thewall thickness of the seal edge portion in order to suppress theincrease in vacuum tensile stress of the seal edge portion caused by theshortening of the skirt portion, it was impossible to achieve the vacuumtensile stress of not more than 8.4 MPa at the weight lighter than thatof Sample 1 which is a conventional example. With regard to Samples 7and 8, the examples of the present invention where the deflection angleof the funnel is set at 110° and 90°, respectively, they presenteddesirable results as is the case of 106° according to the presentinvention.

Table 3 shows data for bulbs consisting of a panel having an effectivescreen diameter along the diagonal axis of the glass panel of 760 mm (32inches), an aspect ratio of 16:9 and a minimum average radius ofcurvature of the outer surface of the face portion of 100,000 mm andfunnels having deflection angels of 103°, 110° and 90°.

In the bulbs for cathode ray tube of Samples 2-5 according to thepresent invention, it was possible to reduce the weight by about 0.5 kgat the maximum compared to the conventional bulb for cathode ray tube asshown by Sample 1, and a desirable result was obtained that the vacuumtensile stress at the seal edge portion was less than the standard valueof 8.4 MPa for all Samples. Furthermore, the bulbs for cathode ray tubeof Samples 2 to 5 according to the present invention were able tosuppress the rate of breakage caused by thermal shock at the time offrit seal heating process better than the conventional bulb for cathoderay tube as shown by Sample 1.

With regard to Samples 4 and 5, since the wall thickness of the sealedge portion was adjusted so as to suppress the increase in vacuumtensile stress of the seal edge portion caused by the shortening of theskirt portion, Samples 4 and 5 became heavier than Sample 3, but weightreduction compared to Sample 1 was realized. With regard to Sample 6which is a comparative example, though an attempt was made to adjust thewall thickness of the seal edge portion in order to suppress theincrease in vacuum tensile stress of the seal edge portion caused by theshortening of the skirt portion, it was impossible to achieve the vacuumtensile stress of not more than 8.4 MPa at the weight lighter than thatof Sample 1 which is a conventional example. With regard to Samples 7and 8, the examples of the present invention where the deflection angleof the funnel is set at 110° and 90°, respectively, they presenteddesirable results as is the case of 103° according to the presentinvention.

Table 4 shows data for bulbs consisting of a panel having an effectivescreen diameter along the diagonal axis of the glass panel of 860 mm (36inches), an aspect ratio of 16:9 and a minimum average radius ofcurvature of the outer surface of the face portion of 50,000 mm andfunnels having deflection angels of 103°, 110° and 90°.

In the bulbs for cathode ray tube of Samples 2-5 according to thepresent invention, it was possible to reduce the weight by about 1.0 kgat the maximum compared to the conventional bulb for cathode ray tube asshown by Sample 1, and a desirable result was obtained that the vacuumtensile stress at the seal edge portion was less than the standard valueof 8.4 MPa for all Samples. Furthermore, the bulbs for cathode ray tubeof Samples 2 to 5 according to the present invention were able tosuppress the rate of breakage caused by thermal shock at the time offrit seal heating process better than the conventional bulb for cathoderay tube as shown by Sample 1.

With regard to Sample 5, since the wall thickness of the seal edgeportion was adjusted so as to suppress the increase in vacuum tensilestress of the seal edge portion caused by the shortening of the skirtportion, Sample 5 became heavier than Sample 4, but weight reductioncompared to Sample 1 was realized. With regard to Sample 6 which is acomparative example, though an attempt was made to adjust the wallthickness of the seal edge portion in order to suppress the increase invacuum tensile stress of the seal edge portion caused by the shorteningof the skirt portion, it was impossible to achieve the vacuum tensilestress of not more than 8.4 MPa at the weight lighter than that ofSample 1 which is a conventional example. With regard to Samples 7 and8, the examples of the present invention where the deflection angle ofthe funnel is set at 110° and 90°, respectively, they presenteddesirable results as is the case of 103° according to the presentinvention.

In the working examples shown in Tables 1 to 4, though the glass wallthickness t of the seal edge surface of the skirt portion is madesmaller than the center wall thickness of the face portion 11, and itcan be understood that a mechanical strength of more than or equal tothe predetermined value can be secured even if the glass wall thicknesst of the seal edge surface of the skirt portion is smaller than thecenter wall thickness of the face portion of the panel for cathode raytube as far as the ratio in the length of the funnel and the skirt ofthe glass bulb for cathode ray tube is within the range defined by thepresent invention.

FIG. 4 is a graph showing the data of Tables 1 and 2 wherein thehorizontal axis represents “θ/2” and the vertical axis represents “H/h”.The symbol Δ represents Sample 1 which is the conventional example, thesymbol ∘ represents glass panels of Samples 2 to 5, 7, 8 according tothe present invention wherein the desired mechanical strength requiredfor a glass bulb and weight reduction were accomplished, and the symbolX represents Sample 6 which is the comparative example wherein thedesired mechanical strength required for a glass bulb and weightreduction were not accomplished. The dotted lines shown in FIG. 4 denotegraphs of: H/h=1/(0.22 tan(θ/2))−1, H/h=1/(0.14 tan(θ/2))−1,respectively.

FIG. 5 is a graph showing the data of Tables 3 and 4 wherein thehorizontal axis represents “θ/2” and the vertical axis represents “H/h”.The symbol Δ represents Sample 1 which is the conventional example, thesymbol ∘ represents glass panels of Samples 2 to 5, 7, 8 according tothe present invention wherein the desired.mechanical strength requiredfor a glass bulb and weight reduction were accomplished, and the symbolX represents Sample 6 which is the comparative example wherein thedesired mechanical strength required for a glass bulb and weightreduction were not accomplished. The dotted lines shown in FIG. 5 denotegraphs of: H/h=1/(0.22 tan(θ/2))−1, H/h=1/(0.16 tan(θ/2))−1,respectively.

In view of FIGS. 4 and 5, the desired mechanical strength required for aglass bulb and weight reduction can be accomplished, and alsosuppressive effects on breakage during frit seal heating process can beaccomplished in the range of 1/(0.22 tan(θ/2))−1≦H/h≦1/(0.14 tan(θ/2))−1in the case where the effective screen diameter D (mm) along thediagonal axis of the glass panel is 510 and 600, that is D is generallyin the range of 500≦D<650, or alternatively in the range of 1/(0.22tan(θ/2))−1≦H/h≦1/(0.16 tan(θ/2))−1 in the case where the effectivescreen diameter D (mm) along the diagonal axis of the glass panel is 760and 860, that is D is generally in more than or equal to 650.

UTILITY IN THE INDUSTRIAL FIELD

According to the glass bulb for cathode ray tube of the presentinvention, excellent effects are accomplished that weight reduction isachieved by shortening the skirt portion of the panel while maintaininga certain mechanical strength as a glass bulb, and that breakage fromthe neighborhood of the seal edge portion along the diagonal axis causedby thermal shock during frit seal heating process and the like can besuppressed.

TABLE 1 Maximum Rate Of Skirt Funnel Wall thickness vacuum breakageSample length length of seal edge tensile Bulb weight Deflection duringfrit No. h (mm) H (mm) surface t (mm) stress (MPa) (kg) angle θ (°)sealing H/h 1 69 201 9.0 4.3 15.7 88 2/10 2.91 2 55 215 9.0 5.9 15.4 880/10 3.91 3 49 221 9.0 7.2 15.1 88 0/10 4.51 4 43 227 10.0 8.3 15.3 880/10 5.28 5 40 230 11.0 8.3 15.6 88 0/10 5.75 6 35 235 12.5 8.5 16.3 880/10 6.71 7 49 135 9.0 8.2 14.3 110 0/10 2.76 8 49 159 9.0 8.0 14.5 1030/10 3.24 Effective screen diameter on diagonal axis: D = 510 mm Minimumvalue of outer surface average radius of curvature: 33,000 mm Centerwall thickness of face portion: 15 mm 1/(0.22 tan(θ/2))-1 : 3.71(θ =88), 2.18(θ = 110), 2.62(θ = 103) 1/(0.14 tan(θ/2))-1 : 6.40(θ = 88),4.00(θ = 110), 4.68(θ = 103)

TABLE 2 Maximum Rate Of Skirt Funnel Wall thickness vacuum breakageSample length length of seal edge tensile Bulb weight Deflection duringfrit No. h (mm) H (mm) surface t (mm) stress (MPa) (kg) angle θ (°)sealing H/h 1 76 157 9.5 7.0 20.7 106 3/10 2.07 2 67 166 9.5 7.5 20.4106 0/10 2.48 3 59 174 9.5 7.9 20.2 106 0/10 2.95 4 51 182 13.0 8.3 20.4106 0/10 3.57 5 45 188 13.0 8.3 20.6 106 0/10 4.18 6 41 192 14.5 8.621.2 106 0/10 4.68 7 59 151 9.5 8.0 19.5 110 0/10 2.56 8 59 241 9.5 7.721.0 90 0/10 4.08 Effective screen diameter on diagonal axis: D = 600 mmMinimum value of outer surface average radius of curvature: 30,000 mmCenter wall thickness of face portion: 14.8 mm 1/(0.22 tan(θ/2))-1 :2.43(θ = 106), 2.18(θ = 110), 3.55(θ = 90) 1/(0.14 tan(θ/2))-1 : 4.38(θ= 106), 4.00(θ = 110), 6.14(θ = 90)

TABLE 3 Maximum Rate Of Skirt Funnel Wall thickness vacuum breakageSample length length of seal edge tensile Bulb weight Deflection duringfrit No. h (mm) H (mm) surface t (mm) stress (MPa) (kg) angle θ (°)sealing H/h 1 86 216 11.5 7.2 37.5 103 2/10 2.51 2 82 220 11.5 7.5 37.3103 0/10 2.68 3 75 227 12.0 7.7 37.0 103 0/10 3.03 4 70 232 13.0 7.937.2 103 0/10 3.31 5 62 240 14.5 8.3 37.4 103 0/10 3.87 6 57 245 15.08.6 37.9 103 0/10 4.30 7 74 192 11.5 8.0 36.1 110 0/10 2.59 8 74 30611.5 7.6 38.1 90 0/10 4.14 Effective screen diameter on diagonal axis: D= 760 mm Minimum value of outer surface average radius of curvature:100,000 mm Center wall thickness of face portion: 19 mm 1/(0.22tan(θ/2))-1 : 2.62(θ = 103), 2.18(θ = 110), 3.55(θ = 90) 1/(0.14tan(θ/2))-1 : 3.97(θ = 103), 3.38(θ = 110), 5.25(θ = 90)

TABLE 4 Maximum Rate Of Skirt Funnel Wall thickness vacuum breakageSample length length of seal edge tensile Bulb weight Deflection duringfrit No. h (mm) H (mm) surface t (mm) stress (MPa) (kg) angle θ (°)sealing H/h 1 97 252 13.5 7.4 53.8 103 2/10 2.60 2 93 256 13.5 7.7 53.6103 0/10 2.75 3 85 264 13.5 8.0 53.1 103 0/10 3.11 4 80 269 14.5 8.252.8 103 0/10 3.36 5 77 272 15.5 8.3 53.7 103 0/10 3.53 6 65 284 17.08.6 54.2 103 0/10 4.37 7 85 216 13.5 8.1 52.0 110 0/10 2.54 8 85 34513.5 7.8 54.5 90 0/10 4.06 Effective screen diameter on diagonal axis: D= 860 mm Minimum value of outer surface average radius of curvature:50,000 mm Center wall thickness of face portion: 20 mm 1/(0.22tan(θ/2))-1 : 2.62(θ = 103), 2.18(θ = 110), 3.55(θ = 90) 1/(0.16tan(θ/2))-1 : 3.97(θ = 103), 3.38(θ = 110), 5.25(θ = 90)

What is claimed is:
 1. A glass bulb for cathode ray tube comprising: aglass panel having a skirt portion continued from a face portion ofapproximately rectangular shape forming an effective screen via a blendR portion; a funnel having a reference line in a yoke portion, thefunnel being sealed with the glass panel; and a neck sealed with thefunnel, to which an electron gun is attached, wherein an effectivescreen diameter D (mm) along a diagonal axis of the face portion of theglass panel is in the range of 500≦D<650; an average radius of curvatureof an outer surface of the face portion is more than or equal to 10,000mm in any radial direction passing the center of the face portion; and alength h (mm) of the skirt portion in a tube axis direction from acontact between an end of the effective screen of an inner surface ofthe face portion and the blend R portion to an edge surface portionwhere the glass panel is sealed with the funnel at least along a shortaxis of the glass panel, a deflection angle θ (°) of the yoke portion ofthe funnel, and a distance H (mm) in the tube axis direction from anedge surface portion where the funnel is sealed with the glass panel tothe reference line satisfy the relationship of: 1/(0.22tan(θ/2))−1≦H/h≦1/(0.14 tan(θ/2))−1.
 2. A glass bulb for cathode raytube comprising: a glass panel having a skirt portion continued from aface portion of approximately rectangular shape forming an effectivescreen via a blend R portion; a funnel having a reference line in a yokeportion, the funnel being sealed with the glass panel; and a neck sealedwith the funnel, to which an electron gun is attached, wherein aneffective screen diameter D (mm) along a diagonal axis of the faceportion of the glass panel is more than or equal to 650; an averageradius of curvature of an outer surface of the face portion is more thanor equal to 10,000 mm in any radial direction passing the center of theface portion; and a length h (mm) of the skirt portion in a tube axisdirection from a contact between an end of the effective screen of aninner surface of the face portion and the blend R portion to an edgesurface portion where the glass panel is sealed with the funnel at leastalong a short axis of the glass panel, a deflection angle θ (°) of theyoke portion of the funnel, and a distance H (mm) in the tube axisdirection from an edge surface portion where the funnel is sealed withthe glass panel to the reference line satisfy the relationship of:1/(0.22 tan(θ/2))−1≦H/h≦1/(0.16 tan(θ/2))−1.